Three component polyol blend for use in insulating rigid polyurethane foams

ABSTRACT

There is now provided a polyisocyanate based rigid closed cell foam made by reacting an organic isocyanate with a polyol composition in the presence of a blowing agent, where the polyol composition contains at least: 
     a) an aromatic amine initiated polyoxyalkylene polyether polyol having an hydroxyl number of 200 meq polyol/g KOH or more; 
     b) an aliphatic amine initiated polyoxyalkylene polyether polyol having an hydroxyl number of 200 meq polyol/g KOH or more; and 
     c) an aromatic polyester polyol having an hydroxyl number of 200 meq. polyol/g KOH or more. 
     The blowing agent is selected from the group consisting of cyclopentane, HFC&#39;s, HCFC&#39;s, and mixtures thereof in an amount of 5.0 weight percent or more based on the weight of the polyol composition. Preferably, the blowing agent is soluble in the polyol composition without sacrificing, and advantageously improving, the thermal insulation and dimensional stability of the resulting polyurethane foam. 
     Also disclosed are a storage stable polyol composition and methods for making a polyisocyanate based rigid closed cell foam.

This is a continuation-in-part of U.S. patent application Ser. No.08/551,507 U.S. Pat. No. 5,547,998; Ser. No. 08/551,658 U.S. Pat. No.5,523,334; and Ser. No. 08/548,362 U.S. Pat. No. 5,525,641, each ofwhich were filed Nov. 1, 1995, and are incorporated herein by reference.

1. FIELD OF THE INVENTION

This invention pertains to rigid closed cell polyurethane foams blownwith a variety of blowing agents. More specifically, the inventionpertains to using a polyol composition in which a variety of blowingagents are useful, and preferably soluble. The polyol composition ismade up of at least an aromatic amine initiated polyoxyalkylenepolyether polyol, an aliphatic amine initiated polyoxyalkylene polyetherpolyol, and an aromatic polyester polyol.

2. BACKGROUND OF THE INVENTION

Various blowing agents, including hydrocarbons among others, are oftenonly partially soluble, if not completely insoluble, in many polyolsused to manufacture rigid polyurethane foams. This is believed to be dueto the non-polar hydrophobic characteristic of hydrocarbons. Theinsolubility or poor shelf life of hydrocarbon-polyol mixtures has, todate, restricted one against storing batches of polyol and hydrocarbonbased blowing agent mixtures for use at a later time. Due to the poorsolubility of various hydrocarbon based blowing agents in polyols, theymust be added to the polyols under constant agitation and immediatelybefore dispensing the foaming ingredients through a mixhead. Theinsolubility of various hydrocarbon based blowing agents also tends tolead to larger, coarser, or uneven cell structures in a polyurethanefoam. As is well known, the thermal conductivity of a foam generallyincreases with a poor cell structure. Therefore, it has been criticalthat the blowing agent(s) employed be uniformly dispersed under constantagitation throughout the polyol mixture immediately prior to foaming inorder to obtain a rigid polyurethane foam having the desired thermalinsulation values.

In U.S. Pat. No. 5,391,317, Smits sought to manufacture a foam havingboth good dimensional stability and thermal insulation usinghydrocarbons as blowing agents. This reference taught the use of aparticular mixture of C₅₋₆ alicyclic alkanes, isopentane and n-pentaneblowing agents in particular molar percents, in combination with apolyol mixture made up of an aromatic initiated polyether polyol, anaromatic polyester polyol, and a different amine initiated polyetherpolyol. As the aromatic initiated polyether polyol, Smits suggestedusing an alkylene oxide adduct of a phenol-formaldehyde resin. Theparticular mixture of alicyclic and isomeric aliphatic alkane blowingagents is taught by Smits as producing a foam having good thermalinsulation values.

The problem of obtaining a closed cell rigid polyurethane foam havingboth good dimensional stability and thermal insulation at low densitieswas also discussed in "An Insight Into The Characteristics of aNucleation Catalyst in HCFC-Free Rigid Foam Systems" by Yoshimura et al.This publication reported the results of evaluations on a host ofcatalysts used in a standard polyurethane formulation to test theeffects of each catalyst on the thermal insulation and dimensionalstability of the foam. The authors noted that the solubility ofcyclopentane in the polyol composition was reduced by increasing theblending ratio of aromatic amine-based polyols. Furthermore, not onlydid the authors note that the solubility of cyclopentane in the polyolswas reduced as the aliphatic amine-initiated polyether polyol contentwas reduced and the aromatic amine-initiated polyether polyol wasincreased, but also noted that no significant effect in thermalconductivity was observed when the aromatic amine-initiated polyetherpolyol content was increased.

3. SUMMARY OF THE INVENTION

It would be highly desirable to provide a polyol composition for makinga dimensionally stable rigid closed cell polyurethane foam from suchpolyol composition having good thermal insulation properties.

Thus, there is now provided a storage stable polyol compositioncomprising a blowing agent and polyol composition containing at least:

a) an aromatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more;

b) an aliphatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more; and

c) an aromatic polyester polyol having an hydroxyl number of 200 meqpolyol/g KOH or more.

The blowing agent(s) utilized with the polyol composition is selectedfrom the group consisting of cyclopentane, HFC's and HCFC's generally,with the amount of blowing agent present being at least about 5.0 weightpercent based on the weight of the polyol composition. Further, theamount of aromatic polyester polyol is 18.0 weight percent or less basedon the weight of the polyol composition. The blowing agent(s) arepreferably soluble in the polyols used in the polyol composition. Theblowing agents employed, and particularly the HFC's and HCFC's, whenused in association with the polyol compositions of the presentinvention have also been found to offer faster demold times for theresulting foams. In addition, the resulting foams typically have lowerdensities, improved K factors, improved thermal insulation propertiesand improved dimensional stabilities over foams produced using otherpolyol systems.

There is also provided a polyisocyanate based rigid closed cell foammade by reacting an organic isocyanate with a polyol composition in thepresence of a blowing agent, where the polyol composition contains atleast:

a) an aromatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more;

b) an aliphatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more;

c) an aromatic polyester polyol having an hydroxyl number of 200 meq.polyol/g KOH or more, in an amount of 18.0 weight percent or less basedon the weight of the polyol composition.

Again, the blowing agent is selected from the group consisting ofcyclopentane, HFC's and HCFC's and is present in an amount of at leastabout 5.0 weight present based on the total weight of the polyolcomposition. By employing these constituents in the polyol composition,the blowing agent is generally soluble in the polyol composition. Thereis also provided a polyurethane foam where the polyol compositioncontains at least one of the aforementioned blowing agents.

The polyol composition preferably will solubilize the blowing agent inthe polyol composition without sacrificing, and advantageouslyimproving, the thermal insulation and dimensional stability of theresulting polyurethane foam. Contrary to Yoshimoto et al., it wassurprising to discover that the aromatic amine initiated polyetherpolyol used in the invention impacted the thermal insulation of thefoam.

There is also provided a method of making a polyisocyanate based rigidclosed cell foam by reacting an organic isocyanate with a polyolcomposition into which is introduced (and preferably dissolved ratherthan emulsified) a blowing agent present in an amount of at least 5.0weight percent or more based on the weight of the polyol composition,and further containing at least:

a) an aromatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more;

b) an aliphatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more; and

c) an aromatic polyester polyol having an hydroxyl number of 200 meq.polyol/g KOH or more, in amount of 18.0 weight percent or less based onthe weight of the polyol composition.

4. DETAILED DESCRIPTION OF THE INVENTION

There is provided a storage stable polyol composition made up of atleast one blowing agent selected from the group consisting ofcyclopentane, HFC's and HCFC's and the polyol composition describedherein. A polyol composition is deemed "storage stable" or "soluble"when the polyol composition has the capacity of retaining the blowingagent in solution or in a dissolved state for a period of at least 5days. The determination of whether or not the blowing agent is insolution or dissolved is measured by mixing the blowing agent with thepolyol composition ingredients in a clear glass jar, capping the jar,and letting the contents remain still for 5 days at room temperaturewithout agitation. If upon visual inspection there is no phaseseparation such that two discrete layers are formed, the blowing agentis deemed soluble in the polyol composition, and the polyol compositionis deemed storage stable.

This test which lasts at least five (5) days is only for purposes ofmeasuring whether a particular polyol composition formulation isadequate to solubilize the blowing agent. As discussed further below,the blowing agent may be added to the polyol composition weeks prior tofoaming, seconds prior to foaming, or right at the mix head. The scopeof the invention includes each of these embodiments. By stating that theblowing agent is soluble in the polyol composition, it is meant that thepolyol composition employed must be capable of solubilizing the blowingagent, and is neither limited to a specific point in the process atwhich the blowing agent is solubilized nor to a time period such as thefive days used for purposes of measuring the capacity of the polyolcomposition for dissolving the blowing agent.

Where it is said that the polyol composition "contains" a blowing agentor that the blowing agent is "dissolved in" or "in solution" with thepolyol composition, this would include those embodiments where theblowing agent is mixed with the other polyol composition ingredients fora period of time sufficient to dissolve the blowing agent in the polyolcomposition prior to introducing the polyol composition into the mixhead for reaction with an organic isocyanate compound, and would notinclude those embodiments where the blowing agent is metered as aseparate stream into a dispensing head for reaction with an organicisocyanate. That is not to say, however, that the blowing agent cannotbe metered as a separate stream for reaction with an organic isocyanateto form the desired product.

The polyol composition contains polyols comprising at least the abovementioned a), b) and c) polyols. Other ingredients that may be includedin the polyol composition are other polyols, catalysts, surfactants,blowing agents, fillers, stabilizers, and other additives. As used inthis specification and in the claims, the term "polyol(s)" includespolyols having hydroxyl, thiol, and/or amine functionalities. The term"polyol(s)" as used herein, however, is limited to compounds containingat least some polyester or polyoxyalkylene groups, and having a numberaverage molecular weight of 200 or more. Where the word "polyol(s)" isused in conjunction with and to modify the words polyether, polyester,or polyoxyalkylene polyether, the word "polyol" is then meant to definea polyhydroxyl functional polyether.

Both the a) and b) polyols are polyoxyalkylene polyether polyols. Thesepolyols may generally be prepared by polymerizing alkylene oxides withpolyhydric amines. Any suitable alkylene oxide may be used such asethylene oxide, propylene oxide, butylene oxide, amylene oxide, andmixtures of these oxides. The polyoxyalkylene polyether polyols may beprepared from other starting materials such as tetrahydrofuran andalkylene oxide-tetrahydrofuran mixtures; epihalohydrins such asepichlorohydrin; as well as aralkylene oxides such as styrene oxide.

Included among the polyether polyols are polyoxyethylene polyols,polyoxypropylene polyols, polyoxybutylene polyols, polytetramethylenepolyols, and block copolymers, for example combinations ofpolyoxypropylene and polyoxyethylene poly-1,2-oxybutylene andpolyoxyethylene polyols, poly-1,4-tetramethylene and polyoxyethylenepolyols, and copolymer polyols prepared from blends or sequentialaddition of two or more alkylene oxides. The polyoxyalkylene polyetherpolyols may be prepared by any known process such as, for example, theprocess disclosed by Wurtz in 1859 and Encyclopedia of ChemicalTechnology, Vol. 7, pp. 257-262, published by Interscience Publishers,Inc. (1951) or in U.S. Pat. No. 1,922,459. The alkylene oxides may beadded to the initiator, individually, sequentially one after the otherto form blocks, or in mixture to form a heteric polyether. Thepolyoxyalkylene polyether polyols may have either primary or secondaryhydroxyl groups. It is preferred that at least one of the amineinitiated polyols, more preferably both the a) and b) polyols, arepolyether polyols terminated with a secondary hydroxyl group throughaddition of, for example, propylene oxide as the terminal block. It ispreferred that one or both of the a) and b) amine initiated polyolscontain 50 weight percent or more, and up to 100 weight percent, ofsecondary hydroxyl group forming alkylene oxides, such aspolyoxypropylene groups, based on the weight of all oxyalkylene groups.This amount can be measured by adding 50 weight percent or more of thesecondary hydroxyl group forming alkylene oxides to the initiatormolecule in the course of manufacturing the polyol.

Suitable initiator molecules for the a) and b) compounds are primary orsecondary amines. These would include, for the a) aromatic amineinitiated polyether polyol, the aromatic amines such as aniline,N-alkylphenylene-diamines, 2,4'-, 2,2'-, and 4,4'-methylenedianiline,2,6- or 2,4-toluenediamine, vicinal toluenediamines, o-chloro-aniline,p-aminoaniline, 1,5-diaminonaphthalene, methylene dianiline, the variouscondensation products of aniline and formaldehyde, and the isomericdiaminotoluenes, with preference given to vicinal toluenediamines.

For the aliphatic amine initiated b) polyol, any aliphatic amine,whether branched or unbranched, substituted or unsubstituted, saturatedor unsaturated, may be used. These would include, as examples, mono-,di, and trialkanolamines, such as monoethanolamine, methylamine,triisopropanolamine; and polyamines such as ethylene diamine, propylenediamine, diethylenetriamine; or 1,3-diaminopropane, 1,3-diaminobutane,and 1,4-diaminobutane. Preferable aliphatic amines include any of thediamines and triamines, most preferably, the diamines.

In at least one embodiment of the present invention, each of the a) andb) polyols have number average molecular weights of 200-750 and nominalfunctionalities of 3 or more. By a nominal functionality, it is meantthat the functionality expected is based upon the functionality of theinitiator molecule, rather than the actual functionality of the finalpolyether after manufacture.

The c) polyol is an aromatic polyester polyol. Suitable polyesterpolyols include those suitable polyester polyols include those obtained,for example, from polycarboxylic acids and polyhydric alcohols. Asuitable polycarboxylic acid may be used such as oxalic acid, malonicacid, succinic acid, glutaric acid, adipic acid, pimelic acid, subericacid, azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleicacid, fumaric acid, glutaconic acid, a-hydromuconic acid, β-hydromuconicacid, a-butyl-a-ethyl-glutaric acid, a,β-diethylsuccinic acid,isophthalic acid, therphthalic acid, phthalic acid, hemimellitic acid,and 1,4-cyclohexanedicarboxylic acid. A suitable polyhydric alcohol maybe used such as ethylene glycol, propylene glycol, dipropylene glycol,trimethylene glycol, 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,7-heptanediol, hydroquinone, resorcinol glycerol, glycerine,1,1,1-trimethylol-propane, 1,1,1-trimethylolethane, pentaerythritol,1,2,6-hexanetriol, a-methyl glucoside, sucrose, and sorbitol. Alsoincluded within the term "polyhydric alcohol" are compounds derived fromphenol such as 2,2-bis(4-hydroxyphenyl)-propane, commonly known asBisphenol A.

The hydroxyl-containing polyester may also be a polyester amide such asis obtained by including some amine or amino alcohol in the reactantsfor the preparation of the polyesters. Thus, polyester amides may beobtained by condensing an amino alcohol such as ethanolamine with thepolycarboxylic acids set forth above or they may be made using the samecomponents that make up the hydroxyl-containing polyester with only aportion of the components being a diamine such as ethylene diamine.

A preferred aromatic polyester polyol useful in accordance with theteachings of the present invention is an alpha-methylglucoside initiatedpolyester polyol derived from polyethylene terephthalate. This polyolhas a molecular weight of approximately 358, a hydroxyl number of about360 meq polyol/g KOH and a nominal average functionality of 2.3.

As alluded to above, each of the polyols a), b) and c) have hydroxylnumbers of 200 or more meq polyol/g KOH. At hydroxyl numbers of lessthan 200, the dimensional stability of the foam begins to deteriorate.The optimum nominal functionality of each amine initiated polyol appearsto be 4 or more, with hydroxyl numbers of 400 or more. Likewise, theoptimum nominal functionality of aromatic polyester polyol appears to be2 or more, with an average hydroxyl numbers of 350 or more.

The overall amount of aromatic polyester polyol c) is 18.0 weightpercent or less and, more preferably, 15.0 weight percent or less basedon the overall weight of all ingredients in the polyol composition.Thus, while the range of polyols a) and b) may vary widely (i.e. fromabout 20.0 to 80.0 weight percent of the polyol composition), under apreferred embodiment the weight ratio of the aromatic amine initiatedpolyol a) to the aliphatic amine initiated polyol b) will be betweenabout 0.8:1.0 to 1.2:1. Therefore, the weight ratio of either polyol a)or b) to the aromatic polyester polyol c) is approximately 3:1 orgreater.

The scope of the invention broadly includes a polyol compositioncontaining the a), b) and c) polyols combined together in a mixture byseparately manufacturing the polyether polyols and the polyester polyol,and subsequently combining the resulting polyols together into amixture. Optionally, the a) and b) polyols can be prepared by aco-initiation method where the aromatic amine and the aliphatic amineinitiators are first blended together, after which the alkylene oxide(s)are added and reacted onto the initiator blend; with the c) polyol beingcombined thereafter. The latter method is the preferred method.

In the latter method, the amount of aliphatic amine initiated polyetherpolyol in the polyol composition would be calculated based on thepercentage of the aliphatic initiator in the initiator blend multipliedby the percentage of the polyether polyol (resulting from addition ofthe alkylene oxide onto the initiator blend) in the polyol composition.

Other polyols besides the a), b), and c) polyols described herein canand preferably are added to the polyol composition. These would includepolythioether polyols, polyester amides and polyacetals containinghydroxyl groups, aliphatic polycarbonates containing hydroxyl groups,amine terminated polyoxyalkylene polyethers, polyester polyols, otherpolyoxyalkylene polyether polyols, and graft dispersion polyols. Inaddition, mixtures of at least two of the aforesaid polyols can be used.The preferable additional polyols are polyoxyalkylene polyether polyolsand/or polyester polyols, however, the total amount of polyester polyolsemployed (including any polyester polyols in addition to polyol c)) willpreferably not exceed 18.0 weight percent based on the total weight ofthe polyol composition.

The additional polyoxyalkylene polyether polyols besides the a) and b)polyols include those initiated with polyhydroxyl compounds. Examples ofsuch initiators are trimethylolpropane, glycerine, sucrose, sorbitol,propylene glycol, dipropylene glycol, pentaerythritol, and2,2-bis(4-hydroxyphenyl)-propane and blends thereof. The preferredpolyols are initiated with polyhydroxyl compounds having at least 4sites reactive with alkylene oxides, and further may be oxyalkylatedsolely with propylene oxide. In a more preferred embodiment, theadditional polyol is a polyoxyalkylene polyether polyol having a nominalfunctionality of 5 or more, which may be initiated with a polyhydroxylcompound. The high functionality serves to increase the crosslinkdensity to provide a dimensionally stable foam.

Suitable polyhydric polythioethers which may be condensed with alkyleneoxides include the condensation product of thiodiglycol or the reactionproduct of a dicarboxylic acid such as is disclosed above for thepreparation of the hydroxyl-containing polyesters with any othersuitable thioether polyol.

Polyhydroxyl-containing phosphorus compounds which may be used includethose compounds disclosed in U.S. Pat. No. 3,639,542. Preferredpolyhydroxyl-containing phosphorus compounds are prepared from alkyleneoxides and acids of phosphorus having a P₂ O₅ equivalency of from about72 percent to about 95 percent.

Suitable polyacetals which may be condensed with alkylene oxides includethe reaction produce of formaldehyde or other suitable aldehyde with adihydric alcohol or an alkylene oxide such as those disclosed above.

Suitable aliphatic thiols which may be condensed with alkylene oxidesinclude alkanethiols containing at least two --SH groups such as1,2-ethanedithiol, 1,2-propanedithiol, 1,2-propanedithiol, and1,6-hexanedithiol; alkene thiols such as 2-butane-1,4-dithiol; andalkene thiols such as 3-hexene-1,5-dithiol.

Also suitable are polymer modified polyols, in particular, the so-calledgraft polyols. Graft polyols are well known to the art and are preparedby the in situ polymerization of one or more vinyl monomers, preferablyacrylonitrile and styrene, in the presence of a polyether polyol,particularly polyols containing a minor amount of natural or inducedunsaturation. Methods of preparing such graft polyols may be found incolumns 1-5 and in the Examples of U.S. Pat. No. 3,652,639; in columns1-6 and the Examples of U.S. Pat. No. 3,823,201; particularly in columns2-8 and the Examples of U.S. Pat. No. 4,690,956; and in U.S. Pat. No.4,524,157; all of which patents are herein incorporated by reference.

Non-graft polymer modified polyols are also suitable, for example, asthose prepared by the reaction of a polyisocyanate with an alkanolaminein the presence of a polyether polyol as taught by U.S. Pat. No.4,293,470; 4,296,213; and U.S. Pat. No. 4,374,209; dispersions ofpolyisocyanurates containing pendant urea groups as taught by U.S. Pat.No. 4,386,167; and polyisocyanurate dispersions also containing biuretlinkages as taught by U.S. Pat. No. 4,359,541. Other polymer modifiedpolyols may be prepared by the in situ size reduction of polymers untilthe particle size is less than 20 mm, preferably less than 10 mm.

The average hydroxyl number of the a), b) and c) polyols in the polyolcomposition should be 200 meq polyol/g KOH or more and, more preferably350 meq polyol/g KOH or more. Individual polyols may be used which fallbelow the lower limit, but the average should be within this range.Polyol compositions whose polyols are on average within this range makegood dimensionally stable foams. In calculating whether the averagehydroxyl number is within this range, by definition only those polyolshaving a number average molecular weight of 200 or more are taken intoaccount.

The amount of additional polyols relative to the a), b) and c) polyolsis not intended to be limited so long as the desired objective ofmanufacturing a dimensionally stable foam having good thermal insulationvalues, and optionally, but preferably solubilizing the blowing agent(s)in the polyol composition can be achieved. In this regard, it isbelieved that the aforementioned objectives can be achieved by using 50weight percent or less of the combined weight of the a), b) and c)polyols, based on the weight of all polyols.

In addition to the foregoing, the invention also includes using at leastone blowing agent selected from the group consisting of cyclopentane,HFC's, HCFC's and mixtures thereof. The blowing agents may be added andsolubilized in the polyol composition for storage and later use in afoaming apparatus or may be added to a preblend tank in the foamingapparatus and preferably solubilized in the polyol compositionimmediately prior to pumping or metering the foaming ingredients to themix head. Alternatively, the blowing agent may be added to the foamingingredients in the mix head as a separate stream, although fullsolubility might be limited due to the short amount of time the blowingagent is exposed to the polyol composition in the mix head. Theadvantage of the polyol composition of the invention is that the polyolcomposition gives one the flexibility of stably storing polyolcompositions containing the desired blowing agent, or solubilizing theblowing agent with the polyol composition in the preblend tank, or, forhowever short a period of time, adding it at the mix head, tomanufacture a foam of the desired quality. We have found that the polyolcomposition of the invention is specially adapted to enable a variety ofblowing agents to be employed including blowing agents selected from thegroup consisting of cyclopentane, HFC's, HCFC's and mixtures thereof toproduce rigid closed cell polyisocyanate based foams meeting the desiredobjectives.

The amount of blowing agent used is 5.0 weight percent or more based onthe weight of the polyol composition. The particular amount of blowingagent(s) will depend in large part upon the desired density of the foamproduct. For most applications, polyurethane free rise densities forthermal insulation applications range from free rise densities of 0.5 to10 pcf, preferably from 1.2 to 2.5 pcf. The preferred overall densitiesof foams packed to 10% by weight, meaning the percentage by weight offoam ingredients above the theoretical amount needed to fill the volumeof the mold upon foaming, are from about 1.2 to about 2.5 pcf, morepreferably from 1.3 to 2.0 pcf. The amount by weight of all blowingagents is generally, based on the polyol composition, from about 5.0weight percent to 40.0 weight percent, and more preferably, 7.0 weightpercent to 36.0 weight percent.

Suitable hydrofluorocarbons, perfluorinated hydrocarbons, andfluorinated ethers (collectively referred to herein as HFC's) which areuseful in accordance with the teachings of the present invention includedifluoromethane (HFC-32); 1,1,1,2-tetrafluoroethane (HFC-134a);1,1,2,2-tetrafluoroethane (HFC-134); 1,1-difluoroethane (HFC- 152a);1,2-difluoroethane (HFC-142), trifluoromethane; heptafluoropropane;1,1,1-trifluoroethane; 1,1,2-trifluoroethane;1,1,1,2,2-pentafluoropropane; 1,1,1,3,3-pentafluoropropane (HFC 245fa);1,1,1,3-tetrafluoropropane; 1,1,2,3,3-pentafluoropropane;1,1,1,3,3-pentafluoro-n-butane; 1,1,1,2,3,3,3-heptafluoropropane (HFC227ea); hexafluorocyclopropane (C-216); octafluorocyclobutane (C-318);perfluorotetrahydrofuran; perfluoroalkyl tetrahydrofurans;perfluorofuran; perfluoropropane, -butane, -cyclobutane, -pentane,-cyclopentane, and -hexane, -cyclohexane, -heptane, and -octane;perfluorodiethyl ether; perfluorodipropyl ether; and perfluoroethylpropyl ether. Preferred among the HFC blowing agents are HFC 134a andHFC 236ea, respectively.

Suitable hydrochlorofluorocarbon blowing agents which may be used inaccordance with the teaching of the present invention are1-chloro-1,2-difluoroethane; 1-chloro-2,2-difluoroethane (142a);1-chloro-1,1-difluoroethane (142b); 1,1-dichloro-1-fluoroethane (141b);1-chloro-1,1,2-trifluoroethane; 1-chloro-1,2,2-trifluoroethane;1,1-diochloro-1,2-difluoroethane; 1-chloro-1,1,2,2-tetrafluoroethane(124a); 1-chloro-1,2,2,2-tetrafluoroethane (124);1,1-dichloro-1,2,2-trifluoroethane; 1,1-dichloro-2,2,2-trifluoroethane(123); and 1,2-dichloro-1,1,2-trifluoroethane (123a);monochlorodifluoromethane (HCFC-22); 1-chloro-2,2,2-trifluoroethane(HCFC-133a); gem-chlorofluoroethylene (R-1131a);chloroheptafluoropropane (HCFC-217); chlorodifluoroethylene (HCFC-1122);and trans-chlorofluoroethylene (HCFC-1131). The most preferredhydrochlorofluorocarbon blowing agent is 1,1-dichloro-1-fluoroethane(HCFC-141b).

The blowing agents which can be used in addition to the blowing agentsselected from the group consisting of cyclopentane, HFC's, HCFC's andmixtures thereof, may be divided into the chemically active blowingagents which chemically react with the isocyanate or with otherformulation ingredients to release a gas for foaming, and the physicallyactive blowing agents which are gaseous at the exotherm foamingtemperatures or less without the necessity for chemically reacting withthe foam ingredients to provide a blowing gas. Included within themeaning of physically active blowing agents are those gases which arethermally unstable and decompose at elevated temperatures.

Examples of chemically active blowing agents are preferentially thosewhich react with the isocyanate to liberate gas, such as CO₂. Suitablechemically active blowing agents include, but are not limited to, water,mono- and polycarboxylic acids having a molecular weight of from 46 to300, salts of these acids, and tertiary alcohols.

Water is preferentially used as a blowing agent. Water reacts with theorganic isocyanate to liberate CO₂ gas which is the actual blowingagent. However, since water consumes isocyanate groups, an equivalentmolar excess of isocyanate must be used to make up for the consumedisocyanates. Water is typically found in minor quantities in the polyolsas a byproduct and may be sufficient to provide the desired blowing froma chemically active substance. Preferably, however, water isadditionally introduced into the polyol composition in amounts from 0.02to 5 weight percent, preferably from 0.5 to 3 weight percent, based onthe weight of the polyol composition.

The organic carboxylic acids used are advantageously aliphatic mono- andpolycarboxylic acids, e.g. dicarboxylic acids. However, other organicmono- and polycarboxylic acids are also suitable. The organic carboxylicacids may, if desired, also contain substituents which are inert underthe reaction conditions of the polyisocyanate polyaddition or arereactive with isocyanate, and/or may contain olefinically unsaturatedgroups. Specific examples of chemically inert substituents are halogenatoms, such as fluorine and/or chlorine, and alkyl, e.g. methyl orethyl. The substituted organic carboxylic acids expediently contain atleast one further group which is reactive toward isocyanates, e.g. amercapto group, a primary and/or secondary amino group, or preferably aprimary and/or secondary hydroxyl group.

Suitable carboxylic acids are thus substituted or unsubstitutedmonocarboxylic acids, e.g. formic acid, acetic acid, propionic acid,2-chloropropionic acid, 3-chloropropionic acid, 2,2-dichloropropionicacid, hexanoic acid, 2-ethyl-hexanoic acid, cyclohexanecarboxylic acid,dodecanoic acid, palmitic acid, stearic acid, oleic acid,3-mercapto-propionic acid, glycolic acid, 3-hydroxypropionic acid,lactic acid, ricinoleic acid, 2-aminopropionic acid, benzoic acid,4-methylbenzoic acid, salicylic acid and anthranilic acid, andunsubstituted or substituted polycarboxylic acids, preferablydicarboxylic acids, e.g. oxalic acid, malonic acid, succinic acid,fumaric acid, maleic acid, glutaric acid, adipic acid, sebacic acid,dodecanedoic acid, tartaric acid, phthalic acid, isophthalic acid andcitric acid. Preferable acids are formic acid, propionic acid, aceticacid, and 2-ethylhexanoic acid, particularly formic acid.

The amine salts are usually formed using tertiary amines, e.g.triethylamine, dimethylbenzylamine, diethylbenzylamine,triethylenediamine, or hydrazine. Tertiary amine salts of formic acidmay be employed as chemically active blowing agents which will reactwith the organic isocyanate. The salts may be added as such or formed insitu by reaction between any tertiary amine (catalyst or polyol) andformic acid contained in the polyol composition.

Combinations of any of the aforementioned chemically active blowingagents may be employed, such as formic acid, salts of formic acid,and/or water.

Physically active blowing agents are those which boil at the exothermfoaming temperature or less, preferably at 50° C. or less. The mostpreferred physically active blowing agents are those which have an ozonedepletion potential of 0.05 or less. Examples of physically activeblowing agents are the volatile non-halogenated hydrocarbons having twoto seven carbon atoms such as alkanes, alkenes, cycloalkanes having upto 6 carbon atoms, dialkyl ethers, cycloalkylene ethers and ketones; anddecomposition products.

Examples of volatile non-halogenated hydrocarbons include linear orbranched alkanes, e.g. butane, isobutane, 2,3 dimethylbutane, n- andisopentane and technical-grade pentane mixtures, n- and isohexanes, n-and isoheptanes, n- and isooctanes, n- and isononanes, n- andisodecanes, n- and isoundecanes, and n- and isododecanes. N-pentane,isopentane or n-hexane, or a mixture thereof are preferably employed asadditional blowing agents. Furthermore, specific examples of alkenes are1-pentene, 2-methylbutene, 3-methylbutene, and 1-hexene, of cycloalkanesin addition to cyclopentane are cyclobutane and cyclohexane, specificexamples of linear or cyclic ethers are dimethyl ether, diethyl ether,methyl ethyl ether, vinyl methyl ether, vinyl ethyl ether, divinylether, tetrahydrofuran and furan, and specific examples of ketones areacetone, methyl ethyl ketone and cyclopentanone. Pure or technical gradecyclopentane may be used, the latter containing about 70 weight percentcyclopentane with the remainder including 2,3 dimethylbutane, pentane,and isopentane. Mixtures of cyclopentane, pentane, and isopentane asdescribed in U.S. Pat. No. 5,391,317 are also included and incorporatedherein by reference.

Decomposition type physically active blowing agents which release a gasthrough thermal decomposition include pecan flour, amine/carbon dioxidecomplexes, and alkyl alkanoate compounds, especially methyl and ethylformates.

Catalysts may be employed which greatly accelerate the reaction of thecompounds containing hydroxyl groups and with the modified or unmodifiedpolyisocyanates. Examples of suitable compounds are cure catalysts whichalso function to shorten tack time, promote green strength, and preventfoam shrinkage. Suitable cure catalysts are organometallic catalysts,preferably organotin catalysts, although it is possible to employ metalssuch as lead, titanium, copper, mercury, cobalt, nickel, iron, vanadium,antimony, and manganese. Suitable organometallic catalysts, exemplifiedhere by tin as the metal, are represented by the formula: R_(n) Sn[X--R¹--Y]₂, wherein R is a C₁ -C₈ alkyl or aryl group, R¹ is a C₀ -C₁₈methylene group optionally substituted or branched with a C₁ -C₄ alkylgroup, Y is hydrogen or an hydroxyl group, preferably hydrogen, X ismethylene, an --S--, an --SR² COO--, --SOOC--, an --O₃ S--, or an--OOC-- group wherein R² is a C₁ -C₄ alkyl, n is 0 or 2, provided thatR¹ is C₀ only when X is a methylene group. Specific examples are tin(II) acetate, tin (II) octanoate, tin (II) ethylhexanoate and tin (II)laurate; and dialkyl (1-8C) tin (IV) salts of organic carboxylic acidshaving 1-32 carbon atoms, preferably 1-20 carbon atoms, e.g., diethyltindiacetate, dibutyltin diacetate, dibutyltin diacetate, dibutyltindilaurate, dibutyltin maleate, dihexyltin diacetate, and dioctyltindiacetate. Other suitable organotin catalysts are organotin alkoxidesand mono or polyalkyl (1-8C) tin (IV) salts of inorganic compounds suchas butyltin trichloride, dimethyl- and diethyl- and dibutyl- anddioctyl- and diphenyl- tin oxide, dibutyltin dibutoxide,di(2-ethylhexyl) tin oxide, dibutyltin dichloride, and dioctyltindioxide. Preferred, however, are tin catalysts with tin-sulfur bondswhich are resistant to hydrolysis, such as dialkyl (1-20C) tindimercaptides, including dimethyl-, dibutyl-, and dioctyl- tindimercaptides.

Tertiary amines also promote urethane linkage formation, and includetriethylamine, 3-methoxypropyldimethylamine, triethylenediamine,tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- andN-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine,N,N,N',N'-tetramethylbutanediamine or -hexanediamine, N,N,N'-trimethylisopropyl propylenediamine, pentamethyldiethylenetriamine,tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea,dimethylpiperazine, 1-methyl-4-dimethylaminoethylpiperazine,1,2-dimethylimidazole, 1-azabicylo[3.3.0]octane and preferably1,4-diazabicylo[2.2.2]octane, and alkanolamine compounds, such astriethanolamine, triisopropanolamine, N-methyl- andN-ethyldiethanolamine and dimethylethanolamine.

To prepare the polyisocyanurate (PIR) and PUR-PIR foams by the processaccording to the invention, a polyisocyanurate catalyst is employed.Suitable polyisocyanurate catalysts are alkali salts, for example,sodium salts, preferably potassium salts and ammonium salts, of organiccarboxylic acids, expediently having from 1 to 8 carbon atoms,preferably 1 or 2 carbon atoms, for example, the salts of formic acid,acetic acid, propionic acid, or octanoic acid, andtris(dialkylaminoethyl)-, tris(dimethylaminopropyl)-,tris(dimethylaminobutyl)- and the correspondingtris(diethylaminoalkyl)-s-hexahydrotriazines. However,(trimethyl-2-hydroxypropyl)ammonium formate,(trimethyl-2-hydroxypropyl)ammonium octanoate, potassium acetate,potassium formate and tris(dimethylaminopropyl)-s-hexahydrotriazine arepolyisocyanurate catalysts which are generally used. The suitablepolyisocyanurate catalyst is usually used in an amount of from 1 to 10parts by weight, preferably from 1.5 to 8 parts by weight, based on 100parts by weight of the total amount of polyols.

Urethane-containing foams may be prepared with or without the use ofchain extenders and/or crosslinking agents, which are not necessary inthis invention to achieve the desired mechanical hardness anddimensional stability. The chain extenders and/or crosslinking agentsused have a number average molecular weight of less than 400, preferablyfrom 60 to 300; or if the chain extenders have polyoxyalkylene groups,then having a number average molecular weight of less than 200. Examplesare dialkylene glycols and aliphatic, cycloaliphatic and/or araliphaticdiols having from 2 to 14 carbon atoms, preferably from 4 to 10 carbonatoms, e.g., ethylene glycol, 1,3-propanediol, 1,10-decanediol, o-, m-,and p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, andpreferably 1,4-butanediol, 1,6-hexanediol,bis(2-hydroxyethyl)hydroquinone, triols such as 1,2,4- and1,3,5-trihydroxycyclohexane, glycerol, and trimethylolpropane.

Polyurethane foams can also be prepared by using secondary aromaticdiamines, primary aromatic diamines, 3,3'-di- and/or 3,3'-,5,5'-tetraalkyl-substituted diaminodiphenylmethanes as chain extendersor crosslinking agents instead of or mixed with the above-mentioneddiols and/or triols.

The amount of chain extender, crosslinking agent or mixture thereofused, if any, is expediently from 2 to 20 percent by weight, preferablyfrom 1 to 15 percent by weight, based on the weight of the polyolcomposition. However, as previously alluded to, it is preferred that nochain extender/crosslinker is used for the preparation of rigid foamssince the polyether polyols described above are sufficient to providethe desired mechanical properties.

If desired, assistants and/or additives can be incorporated into thereaction mixture for the production of the cellular plastics by thepolyisocyanate polyaddition process. Specific examples are surfactants,foam stabilizers, cell regulators, fillers, dyes, pigments,flame-proofing agents, hydrolysis-protection agents, and fungistatic andbacteriostatic substances.

Examples of suitable surfactants are compounds which serve to supporthomogenization of the starting materials and may also regulate the cellstructure of the plastics. Specific examples are salts of sulfonicacids, e.g., alkali metal salts or ammonium salts of dodecylbenzene- ordinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers,such as siloxane-oxyalkylene copolymers and other organopolysiloxanes,oxyethylated alkyl-phenols, oxyethylated fatty alcohols, paraffin oils,castor oil esters, ricinoleic acid esters, Turkey red oil and groundnutoil, and cell regulators, such as paraffins, fatty alcohols, anddimethylpolysiloxanes. The surfactants are usually used in amounts of0.01 to 5 parts by weight, based on 100 parts by weight of the polyolcomponent.

For the purposes of the invention, fillers are conventional organic andinorganic fillers and reinforcing agents. Specific examples areinorganic fillers, such as silicate minerals, for example,phyllosilicates such as antigorite, serpentine, hornblends, amphiboles,chrysotile, and talc; metal oxides, such as kaolin, aluminum oxides,titanium oxides and iron oxides; metal salts, such as chalk, barite andinorganic pigments, such as cadmium sulfide, zinc sulfide and glass,inter alia; kaolin (china clay), aluminum silicate and co-precipitatesof barium sulfate and aluminum silicate, and natural and syntheticfibrous minerals, such as wollastonite, metal, and glass fibers ofvarious lengths. Examples of suitable organic fillers are carbon black,melamine, colophony, cyclopentadienyl resins, cellulose fibers,polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, andpolyester fibers based on aromatic and/or aliphatic dicarboxylic acidesters, and in particular, carbon fibers.

The inorganic and organic fillers may be used individually or asmixtures and may be introduced into the polyol composition or isocyanateside in amounts of from 0.5 to 40 percent by weight, based on the weightof components (the polyol composition and the isocyanate); but thecontent of mats, nonwovens and wovens made from natural and syntheticfibers may reach values of up to 80 percent by weight.

Examples of suitable flameproofing agents are tricresyl phosphate,tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, andtris(2,3-dibromopropyl) phosphate.

In addition to the above-mentioned halogen-substituted phosphates, it isalso possible to use inorganic or organic flameproofing agents, such asred phosphorus, aluminum oxide hydrate, antimony trioxide, arsenicoxide, ammonium polyphosphate (Exolit®) and calcium sulfate, expandablegraphite or cyanuric acid derivatives, e.g., melamine, or mixtures oftwo or more flameproofing agents, e.g., ammonium polyphosphates andmelamine, and, if desired, corn starch, or ammonium polyphosphate,melamine, and expandable graphite and/or, if desired, aromaticpolyesters, in order to flameproof the polyisocyanate polyadditionproducts. In general, from 2 to 50 parts by weight, preferably from 5 to25 parts by weight, of said flameproofing agents may be used per 100parts by weight of the polyol composition.

Further details on the other conventional assistants and additivesmentioned above can be obtained from the specialist literature, forexample, from the monograph by J. H. Saunders and K. C. Frisch, HighPolymers, Volume XVI, Polyurethanes, Parts 1 and 2, IntersciencePublishers 1962 and 1964, respectively, or Kunststoff-Handbuch,Polyurethane, Volume VII, Carl-Hanser-Verlag, Munich, Vienna, 1st and2nd Editions, 1966 and 1983.

Suitable organic polyisocyanates, defined as having 2 or more isocyanatefunctionalities, are conventional aliphatic, cycloaliphatic, araliphaticand preferably aromatic isocyanates. Specific examples include: alkylenediisocyanates with 4 to 12 carbons in the alkylene radical such as1,12-dodecane diisocyanate, 2-ethyl-1,4-tetramethylene diisocyanate,2-methyl-1,5-pentamethylene diisocyanate, 1,4-tetramethylenediisocyanate and preferably 1,6-hexamethylene diisocyanate;cycloaliphatic diisocyanates such as 1,3- and 1,4-cyclohexanediisocyanate as well as any mixtures of these isomers,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate), 2,4- and 2,6-hexahydrotoluene diisocyanate as well as thecorresponding isomeric mixtures, 4,4'- 2,2'-, and2,4'-dicyclohexylmethane diisocyanate as well as the correspondingisomeric mixtures and preferably aromatic diisocyanates andpolyisocyanates such as 2,4- and 2,6-toluene diisocyanate and thecorresponding isomeric mixtures 4,4'-, 2,4'-, and 2,2'-diphenylmethanediisocyanate and the corresponding isomeric mixtures, mixtures of 4,4'-,2,4'-, and 2,2-diphenylmethane diisocyanates andpolyphenylenepolymethylene polyisocyanates (crude MDI), as well asmixtures of crude MDI and toluene diisocyanates. The organic di- andpolyisocyanates can be used individually or in the form of mixtures.Particularly preferred for the production of rigid foams is crude MDIcontaining about 50 to 70 weight percent polyphenyl-polymethylenepolyisocyanate and from 30 to 50 weight percent diphenylmethanediisocyanate, based on the weight of all polyisocyanates used.

Frequently, so-called modified multivalent isocyanates, i.e., productsobtained by the partial chemical reaction of organic diisocyanatesand/or polyisocyanates are used. Examples include diisocyanates and/orpolyisocyanates containing ester groups, urea groups, biuret groups,allophanate groups, carbodiimide groups, isocyanurate groups, and/orurethane groups. Specific examples include organic, preferably aromatic,polyisocyanates containing urethane groups and having an NCO content of33.6 to 15 weight percent, preferably 31 to 21 weight percent, based onthe total weight, e.g., with low molecular weight diols, triols,dialkylene glycols, trialkylene glycols, or polyoxyalkylene glycols witha molecular weight of up to 6000; modified 4,4'-diphenylmethanediisocyanate or 2,4- and 2,6-toluene diisocyanate, where examples of di-and polyoxyalkylene glycols that may be used individually or as mixturesinclude diethylene glycol, dipropylene glycol, polyoxyethylene glycol,polyoxypropylene glycol, polyoxyethylene glycol, polyoxypropyleneglycol, and polyoxypropylene polyoxyethylene glycols or -triols.Prepolymers containing NCO groups with an NCO content of 29 to 3.5weight percent, preferably 21 to 14 weight percent, based on the totalweight and produced from the polyester polyols and/or preferablypolyether polyols described below; 4,4'-diphenylmethane diisocyanate,mixtures of 2,4'- and 4,4'-diphenylmethane diisocyanate, 2,4,- and/or2,6-toluene diisocyanates or polymeric MDI are also suitable.Furthermore, liquid polyisocyanates containing carbodiimide groupshaving an NCO content of 33.6 to 15 weight percent, preferably 31 to 21weight percent, based on the total weight, have also proven suitable,e.g., based on 4,4'- and 2,4'- and/or 2,2'-diphenylmethane diisocyanateand/or 2,4'- and/or 2,6-toluene diisocyanate. The modifiedpolyisocyanates may optionally be mixed together or mixed withunmodified organic polyisocyanates such as 2,4'- and4,4'-diphenylmethane diisocyanate, polymeric MDI, 2,4'- and/or2,6-toluene diisocyanate.

The organic isocyanates used in the invention preferably have an averagefunctionality of greater than 2, most preferably 2.5 or more. Thisprovides for a greater crosslinking density in the resulting foam, whichimproves the dimensional stability of the foam.

To produce the rigid closed cell polyurethane foams of the presentinvention, the organic polyisocyanate and the isocyanate reactivecompounds are reacted in such amounts that the isocyanate index, definedas the number of equivalents of NCO groups divided by the total numberof isocyanate reactive hydrogen atom equivalents multiplied by 100,ranges from 80 to less than 150, preferably from 90 to 110. The polyolcomposition of the invention affords one the flexibility of a largeprocessing window in that the solubility of the polyol composition andthe dimensional stability and thermal insulation of the resulting foamare substantially unaffected throughout a wide range of isocyanateindices. If the rigid foams contain, at least in part, bondedisocyanurate groups,an isocyanate index of 150 to 6000, preferably from200 to 800, is usually used.

In a method of the invention, there is provided the reaction of anorganic isocyanate with a polyol composition containing at least:

a) an aromatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more;

b) an aliphatic amine initiated polyoxyalkylene polyether polyol havingan hydroxyl number of 200 meq polyol/g KOH or more in an amount of 10weight percent or less based on the weight of the polyol composition;

c) an aromatic polyester polyol having an hydroxyl number of 200 meq.polyol/g KOH or more, in an amount of 18.0 weight percent or less basedon the weight of the polyol composition; and

d) a blowing agent selected from the group consisting of cyclopentane,HFC's and HCFC's.

Optionally, but preferably, the hydrocarbon based blowing agent isdissolved in the polyol composition. In one embodiment, the polyolcomposition contains the blowing agent in solution prior to reactionwith the organic isocyanate. Preferably, the organic isocyanate and thepolyol composition are reacted at isocyanate indices ranging from 80 to115. All throughout this range the K-factors of the foam aresubstantially constant and the foams are dimensionally stable. Asubstantially constant K-factor value means that the variance in valuesis ±10 percent or less between the lowest and highest values within therange. Throughout the range, the foam also remains dimensionally stableas defined below. The measurements for the K-factor are taken from coresamples as described below in the definition of a dimensionally stablefoam and are the initial K-factors.

The rigid foams made from polyisocyanate polyaddition products areadvantageously produced by the one-shot process, for example, usingreaction injection moldings, or the high pressure or low pressuremethod, in an open or closed mold, for example, in a metallic mold, orin a pour-in-place application where the surfaces contacting thereaction mixture become a part of the finished article.

The starting components may be mixed at from 15° to 90° C., preferablyat from 20° to 35° C., and introduced into the open or closed mold, ifdesired under super-atmospheric pressure. The mixing of the isocyanatewith the polyol composition containing dissolved blowing agent can becarried out mechanically by means of a stirrer or a stirring screw orunder high pressure by the impingement injection method. The moldtemperature is expediently from 20° to 110° C., preferably from 30° to60° C., in particular from 45° to 50° C.

The rigid foams produced by the process according to the invention andthe corresponding structural foams are used, for example, in the vehicleindustry--the automotive, aircraft, and ship building industries--and inthe furniture and sports goods industries. They are particularlysuitable in the construction and refrigeration sectors as thermalinsulators, for example, as intermediate layers for laminate board orfor foam-filling refrigerators, freezer housings, and picnic coolers.

For pour-in-place applications, the rigid foam may be poured or injectedto form a sandwich structure of a first substrate/foam/second substrateor may be laminated over a substrate to form a substrate foam structure.The first and second substrate may each be independently made of thesame material or of different materials, depending upon the end use.Suitable substrate materials comprise metal such as aluminum, tin, orformed sheet metal such as used in the case of refrigeration cabinets;wood, including composite wood; acrylonitrile-butadiene-styrene (ABS)triblock of rubber, optionally modified with styrene-butadiene diblock,styrene-ethylene/butylene-styrene triblock, optionally functionalizedwith maleic anhydride and/or maleic acid, polyethylene terephthalate,polycarbonate, polyacetals, rubber modified high impact polystyrene(HIPS), blends of HIPS with polyphenylene oxide, copolymers of ethyleneand vinyl acetate, ethylene and acrylic acid, ethylene and vinylalcohol, homopolymers or copolymers of ethylene and propylene such aspolypropylene, high density polyethylene, high molecular weight highdensity polyethylene, polyvinyl chloride, nylon 66, or amorphousthermoplastic polyesters. Preferred are aluminum, tin, ABS, HIPS,polyethylene, and high density polyethylene.

The polyurethane foam may be contiguous to and bonded to the innersurfaces of the first and second substrates, or the polyurethane foammay be contiguous to a layer or lamina of synthetic material interposedbetween the substrates. Thus, the sequence of layers in the compositemay also comprise a first substrate/polyurethane foam/layer orlamina/second substrate or first substrate/layer or lamina/polyurethanefoam/layer or lamina/second substrate.

The layer or lamina of layers additionally interposed into the compositemay comprise any one of the above-mentioned synthetic resins which havegood elongation such as low density polyethylene or low density linearpolyethylene as a stress relief layer or a material which promotesadhesion between the polyurethane foam and the first and/or secondsubstrate of choice.

When a synthetic plastic material such as polyethylene having few or nobonding or adhesion sites is chosen as the first and/or second substrateas an alternative to an adhesion-promoting layer, it is useful to firstmodify the substrate surface with a corona discharge or with a flametreatment to improve adhesion to the polyurethane foam.

During the foam-in-place operation, the substrates are fixed apart in aspaced relationship to define a cavity between the first substrate andsecond substrate, and optionally the inner surface of at least onesubstrate, preferably both, treated to promote adhesion. This cavity isthen filled with a liquid polyurethane system which reacts and foams insitu, bonding to the inner surfaces of the first and second substrates.In the case of a refrigeration unit or a cooler container, such as apicnic cooler, a thermoformed inner liner material is inserted into theouter shell of cooler or the refrigeration cabinet, in a nested spacedrelationship to define a cavity, which cavity is then filled with afoamed-in-place polyurethane foam. In many cases, it is only thepolyurethane foam which holds together the outer shell and inner liner,underscoring the need for foam dimensional stability.

The polyurethane cellular products of the invention are rigid, meaningthat the ratio of tensile strength to compressive strength is high, onthe order of 0.5:1 or greater, and having less than 10 percentelongation. The foams are also closed cell, meaning that the number ofopen cells is 20% or less, or conversely the number of closed cells is80% or greater, the measurement being taken on a molded foam packed at10% over the theoretical amount required to fill the mold with foam.

The rigid polyurethane cellular products of the invention aredimensionally stable, exhibiting little or no shrinkage, even at freerise densities of 2.0 pcf or less. In a preferred embodiment, the rigidpolyurethane cellular products of the invention tested according to ASTMD 2126-87 using core samples of density 2.0 per or less with dimensionsof 3"×3"×1" and taken from a 10% packed boxes measuring 4"×10"×10"advantageously have the following dimensional changes at 28 days ofexposure: at 100° F./100 percent RH, i.e relative humidity, no more than±5 percent, more preferably no more than ±3 percent; at 158° F./100percent RH no more than ±5 percent, most preferably less than ±4percent; at 158° F., dry no more than ±8 percent, preferably no morethan ±6 percent; at 200° F., dry no more than ±5, preferably no morethan ±3percent; and at -20° F. after 7 days exposure no more than ±5percent, preferably no more than ±3 percent.

The thermal insulation values of the rigid closed cell foams accordingto the preferred embodiments of the invention are 0.160 BTU-in./hr.-ft²-F. or less initial, more preferably 0.150 or less initial, measuredfrom the core of a 10% overpacked sample. It has been found that foamsmade with the combination of aliphatic and aromatic amine initiatedpolyether polyols as well as aromatic polyesters polyols exhibitedrelatively low k-factors. Furthermore, it has been found that theblowing agent is only sparingly soluble in polyol compositions whichemploy more than approximately 18.0 weight percent of an aromaticpolyester polyol constituent.

In a preferred embodiment, the rigid polyurethane foams are alsoadvantageously not friable at their surface in spite of their lowdensity and the presence of polyols having a high hydroxyl number andlow equivalent weight. These foams typically exhibit a surfacefriability of less than 5 percent when tested according to ASTM C 421,at core densities of 2.0 pcf or less, even at core densities of 1.5 pcfor less. The low surface friability enables the foam to adhere well tosubstrates.

The term polyisocyanate based foam as used herein is meant to includepolyurethane-polyurea, polyurethane-polyisocyanurate, polyurethane, andpolyisocyanurate foams.

WORKING EXAMPLES

Polyol A is a sucrose-dipropylene glycol co-initiated polyoxypropylenepolyether polyol having a nominal OH number of about 397.

Polyol B is a polyoxyethylene-polyoxypropylene polyether polyolco-initiated with about 90 percent vicinal toluenediamine and about 10percent ethylenediamine, based on the weight of the initiators, thepolyol being terminated with about 68 weight percent oxypropylene groupsbased on the weight of all oxyalkylene groups, and having a nominal OHnumber of about 500.

Polyol C is an alpha-methylglucoside initiated aromatic polyester polyolhaving a nominal OH number of about 360.

POLYCAT®5 is pentamethyl-diethylenetriamine, a catalyst used in thepreparation of rigid foams, commercially available from Air Products.

DMCHA is dimethylcyclohexylamine, commercially available from BASFCorporation.

UL-1 is dibutyltin dimercaptide available from Air Products.

ISO A is polymethylene polyphenylene polyisocyanate having an free NCOcontent of 31.8 percent and a functionality of approximately 2.7.

EXAMPLE 1

The amounts of 45.0 parts by weight of Polyol A, 40.0 parts by weight ofPolyol B, 15.0 parts by weight of Polyol C, 0.9 parts by weight ofPOLYCAT 5, 0.8 parts by weight of DMCHA, 0.1 parts by weight of UL-1,and between 2.0 and 2.5 parts by weight of water depending on theblowing agent employed were blended together. Thereafter, a differentblowing agent as set forth in Table I was added under constant mixing tothe respective polyol compositions.

Each polyol composition, including the differing blowing agents, wasmixed into a 1.5 gallon steel tank and attached to an Edge-Sweets® highpressure impingement mix machine. Varying amounts of ISO A were added tothe different polyol compositions in the isocyanate tank and impingementmixed. The parameters for the Edge-Sweets® high pressure impingement mixmachine were calibrated for consistency and the resulting foams allowedto free rise as set forth in Table I for between 7 and 28 days.

                  TABLE 1                                                         ______________________________________                                        SAMPLE           1       2       3     4                                      ______________________________________                                        Polyol A          45      45      45    45                                    Polyol B          40      40      40    40                                    B-8404            15      15      15    15                                    POLYCAT5          0.90    0.90    0.90  0.90                                  DMCHA             0.60    0.60    0.60  0.60                                  Water             2.0     2.2     2.0   2.5                                   Hydrocarbon Blowing Agents                                                                      14.sup.1                                                                              15.sup.2                                                                              38.sup.3                                                                            35.8.sup.4                            TOTAL            117.5   118.5   138.50                                                                              138.5                                  ISO A            147.23  148.4   145.77                                                                              180                                    Density, F.R. (pcf)                                                                             1.74    1.81    1.68  1.4                                   Initial K-Factor (but/in/hr.ft..sup.2 °F.)                                               0.152   0.148   0.152                                                                               0.138                                 SSC (Percent Vol. Change)                                                     100° F., 100% R.H., 28 days                                                              +1.0    +1.1    -0.5  +2.16                                 158° F., 100% RH 28 days                                                                 +2.1    +0.1    +2.2  +3.31                                 158° F., dry, 28 days                                                                    +0.9    +5.3    0.0   +1.54                                 200° F., dry 28 days                                                                     +2.3    +2.7    +3.7  +2.74                                 200° F., dry 7 days                                                                      +0.3    -1.3    -0.1  +1.1                                  ______________________________________                                         1 -- cyclopentane                                                             2 -- HFC 134a                                                                 3 -- HFC 236 ea                                                               4 -- HCFC 141b                                                           

The dimensional stability of each sample under simulated conditions as afunction of the blowing agent employed as recorded in Table Iillustrates that the three component polyol blend described affords agreat deal of flexibility in choosing a blowing agent for polyurethanefoams for insulation critical applications. Regardless of whether theblowing agent is a hydrocarbon such as cyclopentane, an HFC or HCFC, thepolyol blend described herein when used is a formulated system, providesfor excellent dimensional stability under a number of serviceconditions.

What we claim is:
 1. A storage stable polyol composition comprising:a)an aromatic amine initiated polyoxyalkylene polyether polyol having anhydroxyl number of 200 meq polyol/g KOH or more; b) an aliphatic amineinitiated polyoxyalkylene polyether polyol having an hydroxyl number of200 meq polyol/g KOH or more; c) an aromatic polyester polyol having anhydroxyl number of 200 meq. polyol/g KOH or more; and d) a blowing agentselected from the group consisting of cyclopentane, HFC's, HCFC;s andmixtures thereof;wherein the blowing agent is dissolved in the polyolcomposition.
 2. The composition of claim 1, wherein said c) polyol ispresent in an amount of about 18.0 weight percent or less based on theweight of the polyol composition.
 3. The composition of claim 1, whereinthe amount of blowing agent is at least about 5.0 weight percent basedon the weight of the polyol composition.
 4. The composition of claim 3,wherein said a) and b) polyols together comprise polyols obtained byco-initiating said aromatic amine and said aliphatic amine with analkylene oxide.
 5. The composition of claim 4, wherein said polyolcomposition further comprises an hydroxyl functional polyoxyalkylenepolyether polyol having an average nominal functionality of at least 5.6. The composition of claim 5, wherein the average hydroxyl number ofthe polyols in the polyol composition is at least 350 meq polyol/g KOHor more.
 7. The composition of claim 6, wherein the amount of said a),b) and c) polyols is 50 weight percent or less based on the weight ofall polyols in the polyol composition having a number average molecularweight of at least
 200. 8. The composition of claim 4, wherein each ofsaid a) and b) polyols contain at least 50 weight percent ofpolyoxypropylene groups based on the weight of all oxyalkylene groups.9. The composition of claim 1, wherein said polyol composition furthercomprises water in an amount of from about 0.05 to 4 weight percent. 10.The composition of claim 1, wherein said polyol composition furthercomprises an hydroxyl functional polyoxyalkylene polyether polyol havingan average nominal functionality of at least
 5. 11. The composition ofclaim 1, wherein the average hydroxyl number of all polyols having anumber average molecular weight of at least 200 is at least 350 meqpolyol/g KOH.
 12. The composition of claim 1, wherein the amount of saida), b) and c) polyols is about 50 weight percent or less based on theweight of all polyols in the polyol composition having a number averagemolecular weight of 200 or more.
 13. The composition of claim 1, whereinsaid a) and b) polyols contain at least 50 weight percent ofpolyoxypropylene groups based on the weight of all oxyalkylene groupsemployed in the manufacture of said a) and b) polyols.